Michelson Interferometer

Basic Principle and Practical Use

Michelson Interferometer

Configuration Source produces coherent and monochromatic light

Light is split and reflected from two mirrors, which is detected on a screen

By adjusting a movable mirror, a wavelength can be determined

Two configurations of Interferometer

Two mirrors are strictly

perpendicular

Two mirrors are not strictly

perpendicular

Sample problem

To change the intereference picture to m=500 lines, an adjustable mirror was moved a distance L=0.161mm. Determine the wavelength of light

Solution

We know that L equal to λ/2 corresponds to the shifting of interference pattern by 1 line, so that the general equation is L=m*λ/2

Rearranging this equation gives us λ=2L/m, where L=0.161mm and m=500

Plug in the values into equation: λ=2*0.161*10-4m/500=6.44*10-7m or 644nm (also corresponds to red color)

So, by moving a mirror in Michelson Interferometer we could determine the wavelength of light